Effect of tyrosine kinase inhibition by imatinib mesylate on mast cell tumors in dogs.

BACKGROUND: Imatinib mesylate is a small molecule targeted at dysregulated protein-tyrosine kinase. Mutation of c-kit exon 11, which induces constitutive phosphorylation of KIT, is one of the mechanisms for the development or progression of mast cell tumor (MCT) in dogs. The purpose of this study was to examine the therapeutic potential of imatinib mesylate in canine MCT. HYPOTHESIS: Imatinib mesylate has activity against MCT in dogs, and response to treatment can be correlated to presence of mutation within exon 11 of c-kit. ANIMALS: Twenty-one dogs with MCT with gross tumor burden and median tumor size of 7.2 cm (range, 1.0-25.3 cm) before treatment. METHODS: Tumors were analyzed for mutation of c-kit exon 11. Imatinib mesylate was administered PO to the dogs at a dose of 10 mg/kg daily for 1-9 weeks. RESULTS: Ten of 21 dogs (48%) had some beneficial response to imatinib mesylate treatment within 14 days of treatment initiation. All 5 dogs with a demonstrable c-kit mutation in exon 11 responded to the drug (1 complete remission, 4 partial remission). CONCLUSIONS AND CLINICAL IMPORTANCE: Imatinib mesylate has clinical activity against MCT in dogs. Response could not be predicted based on presence of absence of a mutation in exon 11 of c-kit.

Development of the polymerase chain reaction assay based on the canine genome database for detection of monoclonality in B cell lymphoma.

From the canine genome database and its bioinformatic analysis, we identified conserved sequences within the vast majority of 61 variable segments and 1 joining segment of the immunoglobulin heavy chain (IgH) gene, and designed optimal primers for polymerase chain reaction (PCR) amplification directed at these conserved sequences to evaluate the monoclonality of IgH in canine B cell lymphoma. Using the primers, a PCR-based assay was performed on fine-needle aspiration samples of normal, hyperplasia, and malignant lymph nodes and lymphoma cell lines. All fine-needle aspiration samples of five B cell lymphoma cases and the B cell lymphoma line GL-1 exhibited clonal amplification, whereas no amplification was observed in the samples from normal and hyperplasia lymph nodes, cases of T cell lymphoma, and the T cell lymphoma line CL-1. The primers we designed clearly distinguished malignant B lymphocytes from normal, reactive, and malignant T lymphocytes, indicating a potential utility of the primers for PCR-based routine clinical examination for canine B cell lymphoma.

Identification and gene expression of bovine C-type lectin dectin-2.

The C-type lectin receptor has been shown to recognize carbohydrate moieties of self and non-self antigens, thus serving as an innate immune receptor. Using bioinformatics and molecular cloning techniques, we isolated a bovine gene that encodes a polypeptide of 206 amino acids with structural features shared by mouse and human dectin-2, including a high homology with mouse dectin-2 (66%), a type II configuration, a short cytoplasmic domain without tyrosine-based signal motifs, a carbohydrate recognition domain, a putative N-glycosylation site, and an EPN motif involved in the Ca(2+)-dependent binding of hexose carbohydrates. These results reveal this bovine gene to be a counterpart of mouse dectin-2. Moreover, the bovine dectin-2 gene showed heterogeneity in mRNA (the generation of alternatively spliced transcript) and segmentation into six exons, which are also observed in mouse dectin-2. Inconsistent with mouse dectin-2 mRNA, the bovine counterpart is abundantly expressed by Langerhans cells compared to macrophages; however, lymph nodes showed the highest expression level of bovine dectin-2, while spleen and lung showed the highest expression levels of mouse and human dectin-2. In cattle, dectin-2 expressed by dendritic cells may be clinically involved in the recognition of invading antigens in lymph nodes.

Characterization of cDNA and the genomic sequence encoding canine neural-cell adhesion molecule, CD56/N-CAM.

The neural-cell adhesion molecule, CD56/N-CAM is a member of the immunoglobulin superfamily expressed by various tissues and cells, including natural killer (NK) cells. Despite the importance of CD56 as a marker for identifying NK cells in circulating blood, canine CD56 has not been identified. In the present study, we identified the canine counterparts of the 140-kDa (CD56-140) and 120-kDa (CD56-120) isoforms of human DC56. Both of amino acid sequences encoded by the canine CD56-140 and -120 cDNA showed high homology with those of human (both 96% homology), having well-conserved domains (five immunoglobulin, two fibronectin type III, and transmembrane and intracellular or glycosylphosphatidylinositol-linked domain) among various species (human, mouse, and feline). We revealed that the transcripts of canine CD56-140 and -120 arise from alternative mRNA splicing from a single gene located on canine chromosome 5. Moreover, the mRNA encoding canine CD56-140 was expressed at high levels constitutively by nervous system and endocrine tissues as has shown in other animals.